Wednesday, 31 March 2010

Having been dissatisfied with the way The Pterosaur Database represented the families and species of pterosaurs, I have just completed a re-structuring of the web pages. This is a job in progress, but it should be a little easier to find things. Previously, the pterosaurs were arranged and listed by geological age. This format is still available, but now they are also listed by classification as family groups. This includes time lines for each family extent.The taxonomic list is based loosely on David Unwins classification, with a few alterations to accommodate some of the more recent ideas. It is not possible to please everyone when a classification structure is produced, and that is why I did not do this before. In reality, the analysis of characteristics that leads to a taxonomic structure is quite fluid. Structures may change over time, or be interpreted differently by different researchers, so these pages need to be viewed as useful, but not exclusive.The geological age listing is a little more helpful as I have included continental maps to give an idea of the land masses at different tectonic ages.

At a later date, I intend to update individual pterosaur species pages and endevour to obtain photographs of fossils to add to the text only pages. I would also like to add a world distribution map for each family, but that will take a little more time.

Criticism and recommendations are welcome. If anyone wants to send in photographs, they will be appreciated and credited accordingly.

Sunday, 21 March 2010

The Stonesfield Slate is an interesting deposit which contains quite a lot of fragmentary pterosaur remains. It is one of the few Middle Jurassic deposits in the UK that has yielded pterosaur remains. The pterosaurs of the Middle Jurassic are poorly represented worldwide, so this is an important source of information on the species that were around at that time. It is clear that this age had a very rich pterosaur fauna, as a large number of species are represented by bone fragments, some of which are specific to this time.

One such genus is Rhamphocephalus, which is known from a few jaw, tooth and wing bone remains. It is uncertain that the jaws and wing bones are from the same species, so they are assigned differently.Rhamphocephalus depresirostris is known from a distal lower jaw fragment and a few isolated teeth. The jaw is unlike any other pterosaur. Two dissociated wing bones are also assigned to this species. Another few wing bones are assigned to Rhamphocephalus bucklandi along with another different jaw fragment.A further specimen of an upper skull bone is assigned as Rhamphocephalus prestwichi.There are many remains from the Stonesfield Slate, including individual bones from Dimorphodon, Anurognathus, Pterodactylus and other species.

Friday, 12 March 2010

Identifying pterosaur teeth is not easy, especially from photographic evidence. The five teeth below were extracted from my own fossil collection to illustrate the difficulty in knowing that you have a pterosaur fossil tooth. They are all authenticated specimens.

Many fossil species show a variation in tooth structure throughout the jaw. In the case of 3 - the tooth from the crocodile Steniosaurus durobreviensis, most of the teeth show little resemblance to pterosaur teeth, but in this case, a few broken teeth from the mid jaw could easily be confused if seen in isolation. I used to live near to the quarry where this specimen was found.

Saturday, 6 March 2010

Following on from my last post, I thought it would be interesting to give readers a chance to look at some teeth pictures. This should test even the most experienced eye as it is always difficult to examine teeth from photographs. The photo below is of some of the teeth in my own collection of fossils. Tooth 1 is 3.5 cm long for scale.Question:- which teeth are pterosaur and which teeth are non-pterosaur?

You may even like to suggest a family or species for each tooth. Answers will follow in a future post.